The process according to the invention applies to the simultaneous exchange of heat and matter.
It can be used particularly for effecting exchange between hot and moist gas which is cooled by transferring heat and condensed water to a colder and dryer gas which becomes charged with steam in being heated.
Such simultaneous exchange of heat and of matter has already been done in different ways in the prior art.
FIG. 1 shows a first known method of operating.
A hot and moist gas arrives through the pipe 1 into a packed column G1 in which it is contacted with a flow of colder water arriving through the pipe 2. The gas emerges cooled through the pipe 3. The cooling causes an additional condensation of water which is removed through the pipe 4 and is taken up by the pump P1 at the same time as the cooling water at the bottom of the packed column G1.
The water thus heated is contacted in a packed column G2 with a colder and dryer gas which arrives through the pipe 5. The gas emerges heated through the pipe 6 becoming charged with water in the course of the contact which took place in the packed column G2.
The water collected at the bottom of the packed column G2 is removed through the pipe 7 and is taken up by the pump P2.
This device has the drawback of being cumbersome and requiring two circulating pumps.
It has been discovered that it is possible to avoid these drawbacks by using the process according to the invention.
This process of simultaneous transfer of heat and of matter from a relatively hot gaseous phase (I) to a relatively cold gaseous phase (II), the gaseous phase (I) comprising at least two constituents A and B having different condensation temperatures, the condensation temperature of A being lower than the condensation temperature of B and at least the constituent B being at least in part condensable under the conditions of the process, is characterized in that the gaseous phase (I) is circulated in contact with the first surface of an exchange wall permeable at least to the constituent B in the liquid state, in that the gaseous phase (II) is circulated in contact with the second surface of the porous exchange wall, in a direction substantially parallel and opposite that of the flow of the gaseous phase (I), the temperature of the gaseous phase (II) at the start of the contact being sufficiently low to permit the condensation of at least one fraction of the constituent B of the gaseous phase (I) and the maintenance of the resulting condensate in at least a part of the thickness of the porous part of the exchange wall, the temperature of the gaseous phase (II) not however being too low to avoid a total condensation of the constituents A and B of said gaseous phase (I) in the course of said contact, the pressure conditions on each side of the wall being mutually adapted to permit said condensation of a fraction of the constituent B on said first surface and the vaporisation of said condensed fraction on said second surface, and in that the gaseous phase (I) of lower temperature of lowered concentration of constituent B and of increased concentration of constituent A, and the gaseous phase (II) of increased temperature and concentration in constituent B, are withdrawn separately.